Partially embedding Pt nanoparticles in the skeleton of 3DOM Mn2O3: An effective strategy for enhancing catalytic stability in toluene combustion

Abstract

Polymethyl methacrylate-templating and ethylene glycol reduction methods were adopted to prepare the nanosized Pt catalysts (x wt% Pt/3DOM Mn2O3; x = 0.2–2.3) that were partially embedded in the skeleton of three-dimensionally ordered macroporous (3DOM) Mn2O3. These materials possessed a surface area of 33–36 m2/g, with the Pt NPs (3.6–4.4 nm in size) being well embedded in the skeleton of 3DOM Mn2O3. The 2.3 wt% Pt/3DOM Mn2O3 sample showed the best activity and the lowest apparent activation energy (41 kJ/mol) for toluene combustion, which was related to its high adsorbed oxygen species concentration and good low-temperature reducibility. Compared with 2.0 wt% Pt/3DOM Mn2O3-imp derived from the colloid adsorption method, 2.3 wt% Pt/3DOM Mn2O3 exhibited a better catalytic stability within 60 h of toluene combustion. After calcination at 650 °C for 3 h, the average particle size of Pt nanoparticles (NPs) in 2.3 wt% Pt/3DOM Mn2O3 grew up slightly from 4.3 to 4.9 nm and toluene conversions decreased slightly, while that of Pt NPs in 2.0 wt% Pt/3DOM Mn2O3-imp increased greatly from 4.4 to 13.7 nm and toluene conversions dropped significantly. Effects of H2O, CO2, and SO2 on activity of 2.3 wt% Pt/3DOM Mn2O3 and 2.0 wt% Pt/3DOM Mn2O3-imp were also examined. Partial deactivation induced by H2O or CO2 addition was reversible, whereas that due to SO2 introduction was irreversible. It is concluded that the strong interaction between Pt NPs and 3DOM Mn2O3 was responsible for excellent stability of the partially Pt-embedded 3DOM Mn2O3 sample in toluene combustion.